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1、项目介绍

Flutter 是目前比较流行的跨平台开发技术，凭借其出色的性能获得很多前端技术爱好者的关注，比如 阿里闲鱼 ， 美团 ， 腾讯 等大公司都有投入相关案例生产使用。

flutter_chatroom项目 是基于 Flutter+Dart+chewie+photo_view+image_picker 等技术开发的跨平台仿微信app聊天界面应用，实现了消息/表情发送、图片预览、长按菜单、红包/小视频/朋友圈等功能。

2、技术框架

• 使用技术：Flutter 1.12.13/Dart 2.7.0
• 视频组件：chewie: ^0.9.7
• 图片/拍照：image_picker: ^0.6.6+1
• 图片预览组件：photo_view: ^0.9.2
• 弹窗组件：showModalBottomSheet/AlertDialog/SnackBar
• 本地存储：shared_preferences: ^0.5.7+1
• 字体图标：阿里iconfont字体图标库

鉴于flutter基于dart语言，需要安装 Dart Sdk / Flutter Sdk ，至于如何搭建开发环境，可以去官网查阅文档资料

https://flutter.cn/

https://flutterchina.club/

https://pub.flutter-io.cn/

https://www.dartcn.com/

使用vscode编辑器，可先安装 Dart 、 Flutter 、 Flutter widget snippets 等扩展插件

3、flutter沉浸式状态栏/底部tabbar

flutter中如何实现顶部全背景沉浸式透明状态栏(去掉状态栏黑色半透明背景)，去掉右上角banner，可以去看这篇文章

https://segmentfault.com/a/11...

4、flutter图标组件/IconData自定义封装组件

Icon(Icons.search) 
Icon(IconData(0xe60e, fontFamily:'iconfont'), size:24.0)

使用第二种方式需要先下载阿里图标库字体文件，然后在pubspec.yaml中引入字体

class GStyle {// __ 自定义图标static iconfont(int codePoint, {double size = 16.0, Color color}) {return Icon(IconData(codePoint, fontFamily: 'iconfont', matchTextDirection: true),size: size,color: color,);}
}

调用非常简单，可自定义颜色、字体大小；

GStyle.iconfont(0xe635, color: Colors.orange, size: 17.0)

5、flutter实现badge红点/圆点提示

如上图：在flutter中没有圆点提示组件，需要自己封装实现；

class GStyle {// 消息红点static badge(int count, {Color color = Colors.red, bool isdot = false, double height = 18.0, double width = 18.0}) {final _num = count > 99 ? '···' : count;return Container(alignment: Alignment.center, height: !isdot ? height : height/2, width: !isdot ? width : width/2,decoration: BoxDecoration(color: color, borderRadius: BorderRadius.circular(100.0)),child: !isdot ? Text('$_num', style: TextStyle(color: Colors.white, fontSize: 12.0)) : null);}
}

支持自定义红点大小、颜色，默认数字超过99就...显示；

GStyle.badge(0, isdot:true)
GStyle.badge(13)

GStyle.badge(29, color: Colors.orange, height: 15.0, width: 15.0)

6、flutter长按自定义弹窗

• 在flutter中如何实现长按，并在长按位置弹出菜单，类似微信消息长按弹窗效果；

通过 InkWell 组件提供的 onTapDown 事件获取坐标点实现

InkWell(splashColor: Colors.grey[200],child: Container(...),onTapDown: (TapDownDetails details) {_globalPositionX = details.globalPosition.dx;_globalPositionY = details.globalPosition.dy;},onLongPress: () {_showPopupMenu(context);},
),

// 长按弹窗
double _globalPositionX = 0.0; //长按位置的横坐标
double _globalPositionY = 0.0; //长按位置的纵坐标
void _showPopupMenu(BuildContext context) {// 确定点击位置在左侧还是右侧bool isLeft = _globalPositionX > MediaQuery.of(context).size.width/2 ? false : true;// 确定点击位置在上半屏幕还是下半屏幕bool isTop = _globalPositionY > MediaQuery.of(context).size.height/2 ? false : true;showDialog(context: context,builder: (context) {return Stack(children: <Widget>[Positioned(top: isTop ? _globalPositionY : _globalPositionY - 200.0,left: isLeft ? _globalPositionX : _globalPositionX - 120.0,width: 120.0,child: Material(...),)],);});
}

• flutter如何实现去掉AlertDialog弹窗大小限制？

可通过 SizedBox 和无限制容器 UnconstrainedBox 组件实现

void _showCardPopup(BuildContext context) {showDialog(context: context,builder: (context) {return UnconstrainedBox(constrainedAxis: Axis.vertical,child: SizedBox(width: 260,child: AlertDialog(content: Container(...),elevation: 0,contentPadding: EdgeInsets.symmetric(horizontal: 10.0, vertical: 20.0),),),);});
}

7、flutter登录/注册表单|本地存储

flutter提供了两个文本框组件： TextField 和 TextFormField
本文是使用 TextField 实现，并在文本框后添加清空文本框/密码查看图标

TextField(keyboardType: TextInputType.phone,controller: TextEditingController.fromValue(TextEditingValue(text: formObj['tel'],selection: new TextSelection.fromPosition(TextPosition(affinity: TextAffinity.downstream, offset: formObj['tel'].length)))),decoration: InputDecoration(hintText: "请输入手机号",isDense: true,hintStyle: TextStyle(fontSize: 14.0),suffixIcon: Visibility(visible: formObj['tel'].isNotEmpty,child: InkWell(child: GStyle.iconfont(0xe69f, color: Colors.grey, size: 14.0), onTap: () {setState(() { formObj['tel'] = ''; });}),),border: OutlineInputBorder(borderSide: BorderSide.none)),onChanged: (val) {setState(() { formObj['tel'] = val; });},
)TextField(decoration: InputDecoration(hintText: "请输入密码",isDense: true,hintStyle: TextStyle(fontSize: 14.0),suffixIcon: InkWell(child: Icon(formObj['isObscureText'] ? Icons.visibility_off : Icons.visibility, color: Colors.grey, size: 14.0),onTap: () {setState(() {formObj['isObscureText'] = !formObj['isObscureText'];});},),border: OutlineInputBorder(borderSide: BorderSide.none)),obscureText: formObj['isObscureText'],onChanged: (val) {setState(() { formObj['pwd'] = val; });},
)

验证消息提示则是使用flutter提供的SnackBar实现

// SnackBar提示
final _scaffoldkey = new GlobalKey<ScaffoldState>();
void _snackbar(String title, {Color color}) {_scaffoldkey.currentState.showSnackBar(SnackBar(backgroundColor: color ?? Colors.redAccent,content: Text(title),duration: Duration(seconds: 1),));
}

另外本地存储使用的是 shared\_preferences ，至于如何使用可参看

https://pub.flutter-io.cn/packages/shared_preferences

void handleSubmit() async {if(formObj['tel'] == '') {_snackbar('手机号不能为空');}else if(!Util.checkTel(formObj['tel'])) {_snackbar('手机号格式有误');}else if(formObj['pwd'] == '') {_snackbar('密码不能为空');}else {// ...接口数据// 设置存储信息final prefs = await SharedPreferences.getInstance();prefs.setBool('hasLogin', true);prefs.setInt('user', int.parse(formObj['tel']));prefs.setString('token', Util.setToken());_snackbar('恭喜你，登录成功', color: Colors.greenAccent[400]);Timer(Duration(seconds: 2), (){Navigator.pushNamedAndRemoveUntil(context, '/tabbarpage', (route) => route == null);});}
}

8、flutter聊天页面功能

• 在flutter中如何实现类似上图编辑器功能？通过TextField提供的多行文本框属性 maxLines 就可实现。

Container(margin: GStyle.margin(10.0),decoration: BoxDecoration(color: Colors.white, borderRadius: BorderRadius.circular(3.0)),constraints: BoxConstraints(minHeight: 30.0, maxHeight: 150.0),child: TextField(maxLines: null,keyboardType: TextInputType.multiline,decoration: InputDecoration(hintStyle: TextStyle(fontSize: 14.0),isDense: true,contentPadding: EdgeInsets.all(5.0),border: OutlineInputBorder(borderSide: BorderSide.none)),controller: _textEditingController,focusNode: _focusNode,onChanged: (val) {setState(() {editorLastCursor = _textEditingController.selection.baseOffset;});},onTap: () {handleEditorTaped();},),
),

• flutter实现滚动聊天信息到最底部

通过ListView里controller属性提供的 jumpTo 方法及 _msgController.position.maxScrollExtent

ScrollController _msgController = new ScrollController();
...
ListView(controller: _msgController,padding: EdgeInsets.all(10.0),children: renderMsgTpl(),
)// 滚动消息至聊天底部
void scrollMsgBottom() {timer = Timer(Duration(milliseconds: 100), () => _msgController.jumpTo(_msgController.position.maxScrollExtent));
}

行了，基于flutter/dart开发聊天室实例就介绍到这里，希望能喜欢~~:muscle::muscle:

最后附上electron桌面端应用实例

electron聊天室|vue+electron-vue仿微信客户端|electron桌面聊天